Apparatus for taking a continuous x-ray picture of the dental arch

ABSTRACT

Apparatus for taking a continuous X-ray picture of the dental arch wherein an X-ray tube and a film holder are held in a spaced apart relation and moved about a patient&#39;&#39;s jaws along an elliptical arc. As the film holder is moved, it is automatically rotated about its own axis so that unexposed portions of the film on the outer lateral circumferential surface of the film holder are successively caused to face the X-ray tube.

O United States Patent [1 1 [111 3,867,636

Miyahara Feb. 18, 1975 APPARATUS FOR TAKlNG A CONTINUOUS [56] References Cited X-RAY PICTURE OF THE DENTAL ARCH UNITED STATES PATENTS [75] Inventor: Masato Miyahara, Kyoto, Japan 3,536,913 10/1970 Hachel 250/491 3,636,349 l/l972 Faude 99/470 [73] Asslgneeg l z 'f z z' g gggg 3,673,408 6/1972 Moss 250/491 elsa us yo [22] Filed: Mar. 15, 1974 Primary Examiner.lames W. Lawrence Assistant Examiner-C. E. Church [21] Appl' 451507 Attorney, Agent, or FirmChristensen, OConnor,

Related US. Application Data Garrison & Havelka [63] Continuation of Ser. No, 327,656, Jan, 29, 1973,

abandoned, and a continuation-in-part of Ser. No. [57] ABSTRACT 301124 1972' Apparatus for taking a continuous X-ray picture of the dental arch wherein an X-ray tube and a film holder [30] Foreign Apphcatlon Prmmy Data are held in a spaced apart relation and moved about a May 29, 1972 Japan 47-53166 patients j along an elliptical arc As the holder is moved, it is automatically rotated about its [22] 250/42563i52/l5/i2 Own axis so that unexposed portions of the film on the 1 outer lateral circumferential surface of the film holder [5 8] held of Search 250/444 3267 are successively caused to face the X-ray tube..

10 Claims, 7 Drawing Figures APPARATUS FOR TAKING A CONTINUOUS X-RAY PICTURE OF THE DENTAL ARCH RELATED APPLICATION The present application is a continuation of application Ser. No. 327,656, filed .Ian. 29, 1973 and now abandoned and a continuation-in-part of my earlierfiled, copending application Ser. No. 303,l24, entitled Apparatus for Taking a Continuous X-ray Picture of the Dental Arch and filed on Nov. 1, 1972.

BACKGROUND OF THE INVENTION holder are moved. As the tube and film holder are' moved in this manner, it is necessary to bring unexposed portions of the film successively and in synchronism with the movement of the tube and film holder into the position where they are exposed to the X-ray from the tube, and the mechanism therefor is very complex.

Accordingly, it is one object of the invention to provide for an apparatus for taking a continuous X-ray picture of the dental arch, a simple mechanism for causing unexposed portions of a film to be successively exposed to the X-ray from the tube.

Another object of the invention is to provide such a mechanism as aforesaid which is operated in synchronism with the movement of the X-ray tube and the film holder.

Another object of the invention is to provide an apparatus for taking a continuous X-ray picture of the dental arch, which comprises a rotatable cylindrical film holder around which a film is wound; means for moving the film holder along an elliptical arc; and means for rotating the film holder about its own axis in synchronism with movement of the film holder along the elliptical arc, so that the unexposed portions of the film on the film holder are successively brought into a position where they are exposed to the X-ray from the tube.

Still another object of the invention is to provide such an apparatus as aforesaid, wherein the drive for rotation of the film holder about its axis is provided by the movement of the holder along the elliptical are, so that no particular drive is required for the rotation of the film holder.

SUMMARY OF THE INVENTION In one preferred embodiment of the invention, there is provided a support arm which has at one end thereof an X-ray tube and at the opposite end a film holder about the outer lateral circumference of which a film is wound. The arm is turned by any suitable means so that each and every point thereon moves along an elliptical arc. There is provided another arm which crosses the first arm. As the first arm is turned, the angle between the first and second arms changes, with corresponding change in the relative position of the two arms. The second arm has a cam fixed thereto, which is in frictional contact with a roller fixed to the shaft of the film holder. A point on the second arm is always positioned on the axis of an ellipse along which the first arm is turned. With this arrangement, the angle of interception of the two arms will vary as the first arm is turned. As the first arm is turned, the second arm also is turned, with resulting change in the point of contact of the roller with the cam. This change causes the roller to be rotated. Thus, the film holder is rotated about its own axis as it is moved along an elliptical arc. By selecting the shape of the cam it is possible to have a desired speed of rotation of the film for the same speed of turning of the arm.

In order that a point on the second arm is always positioned on the axis of the ellipse along which the arm is moved, there may be provided a groove which extends along, say, the long axis of the ellipse, so that a roller carried on the second arm may be engaged in the groove to roll therein. Alternatively, on an extension of the long axis of the ellipse there may be provided a pin which is slidably engaged in a slot formed longitudinally in the second arm.

The cam fixed to the second arm is urged by a spring against the roller fixed to the shaft of the film holder, so that as the roller is moved along an elliptical arc, the second arm is longitudinally displaced as it is turned along an elliptical arc, with the roller or the pin on the second arm sliding along the groove.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more clearly understood by reading the following description with reference to the accompanying drawings, wherein:

FIG. I is a top plan view of one embodiment of the invention;

FIG. 2 is a side view, partly in cross-section, of the deviceof FIG. 1;

FIG. 3 is a top plan view, on an enlarged scale, of a portion of the device of FIG. 1;

FIG. 4 is a side view of FIG. 3; and

FIG. 5 is a top plan view of another embodiment of the invention.

FIGS. 6 and 7 show various shapes of cams that may be used to engage the film holder and the corresponding film holder paths that result therefrom.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is shown the device of the invention as combined with a mechanism for turning the X-ray tube and the film along an elliptical arc. First this mechanism will be explained.

A base I has an annular plate 2 fixed thereon. On the upper side of the base 1 and within the annular plate 2 there is provided a guide plate 3, on the upper surface of which there are formed a pair of ellipsographic guide paths in the form of grooves 4 and 5 crossing each other perpendicularly. The groove 4 is less deep than the groove 5.

A pair of slidable members 6 and 7 are provided in the grooves 4 and 5, respectively, so that they can move therein with their under surfaces in sliding contact with the bottom surfaces of the grooves. The slidable member 7 in the deeper groove 5 is of such a height that its upper surface does not rise above the bottom surface of the other groove 4.

The slidable members 6 and 7 are provided with pins 8 and 9, respectively, standing upright thereon, and an arm is pivotally connected to the pins 8 and 9 at two longitudinally spaced apart positions on the arm. The pins 8 and 9 may be rigidly fixed to the arm 10 provided that they are pivotally connected to the slidable members 6 and 7. An X-ray tube 11 depends from one end of the arm, from the other end of which a cylindrical film holder l2'depends. A film is wound around the outer circumferential surface of the film holder. The arm 10 is provided with a roller 14 which is driven by a motor 13 fixed to the under side of the arm.

As the roller 14 is rotated by the motor 13, it rolls on the upper surface of the plate 2, so that the arm 10 is turned in a plane parallel with the upper surface of the plate 2. The turning movement of the arm is effected in such a manner alone that the slidable members 6 and 7 move in the grooves 4 and 5. Since the grooves cross each other perpendicularly and the distance between the pins 8 and 9 remains unchanged, the arm 10 is turned so that any point thereon moves along the arc of an ellipse the long and short axes of which are parallel with the grooves 4 and 5, respectively. Thus, the film holder 12 is moved along an elliptical path P.

The patient is positioned between the X-ray tube 11 and the film holder 12, with his or her head held motionless adjacent to and toward the film holder. Under the condition, as the arm is turned in the direction of an arrow A, with the X-ray tube starting from one side of the patients head to pass the back side thereof as far as the opposite side thereof, a continuous X-ray picture of the dental arch of the patient can be taken.

It should be noted that any other suitable mechanism than the one illustrated may be employed for moving the arm along an elliptical path.

In accordance with the invention, there is provided a fixed reference or guide arm 22 extending in the same direction as the groove 4 or the long axis of the ellipse P which the film holder 12 traces as the arm 10 is turned in the above-mentioned manner. A longitudinal slot 21 is formed in the fixed arm 22. There is a link or second movable arm 23 having at one end thereof a roller 24 slidably engaged in the slot 21 of the arm 22 to form a cam connection therebetween. The opposite end of the arm 23 is formed into a cam 25 having a shaft 26 positioned just above the axis of the arm 10. Pivotally connected to the shaft 26 is a link or lever 29 which is pivotally connected in turn about a pin 28 fixed to a lateral tongue 27 secured to the arm 10. The cam 25 has its curvilinear peripheral surface urged against the peripheral surface of a wheel-like disk or roller 31 fixed to the shaft of the film holder 12. To this end a spring 32 is provided between the lever 29 and a finger 27' fixed to the lateral tongue 27 to urge the lever 29 clockwise in FIG. 3 and consequently press angle between the arms 10 and 23 decreases with the roller 24 moving rightward in FIG. 1 in the slot 21, until both arms lie parallel with the groove 4. The relative movement of the two arms 10 and 23 causes the contacting point of the cam 25 on the disk 31 to change, thereby rotating the disk 31 counterclockwise in FIG.

1 as indicated by an arrow B. This rotation of the disk 31 continues as the arm is farther turned beyond the groove 4. In other words, so far as the arm 10 is turned in one and the same direction, the roller 31 is rotated in one and the same direction. The rotation of the disk 31 results in rotation of the film holder 12 in the same direction. Thus, as the arm 10 is turned, the film holder 12 is rotated so that unexposed portions of the film on the film holder are successively caused to face the X-ray tube.

FIG. 5 shows another embodiment of the invention. Here, the mechanism for turning the arm is the same as shown in FIG. 1. In FIG. 5, however, on a tongue 42 secured to the guide plate 2 there is fixed a pin 41 on a straight line extending from the axis of the groove 4. The arm 23 is formed with a longitudinal slot 43 in which a pin 41 slidably engages. It will be easily seen that as the arm 10 is turned, the angle between the arms 10 and 23 changes so that the disk 31 rotated in the same manner as previously mentioned.

In the illustrated embodiments, the shape of the cam is of a circular shape. By changing the shape of the cam it is possible even with the same speed of the rotation of the arm 10 to change the rotational angular speed of the disk 31 and consequently the film holder with res'pect to the turning speed of the arm, thereby changing the tomographic path along which the X-ray picture is to be taken. FIG. 6 shows the relation of three different shapes of the cam to the tomographic paths resulting therefrom. By changing the length of the second arm it is also possible to change the tomographic path as shown in FIG. 7. Thus, in accordance with the invention it is possible to obtain a tomographic path most suitable for the dental arch whose X-ray picture is to be taken.

What I claim is:

1. In apparatus for recording a continuous X-ray picture of the dental arch, a fixed base, a drive member which is mounted to rotate opposite the base, and which is equipped with an X-ray source and an X-ray film holder on opposite sides of the rotational axis thereof, means operable to rotate the drive member, means operable during the rotation of the drive member to cause the rotational axis of the drive member to shift in relation to the base such that the source and the holder trace coaxial elliptical arcs, a fixed reference, and a pair of pivotally interconnected links, a first of which is pivotally connected with the drive member, and the second of which is cam connected with the reference, said film holder being rotatably mounted on the drive member, and there being a cam fixed on one of the links, and means on the drive member yieldably biasing the cam into engagement with the film holder so that on rotation of the drive member, the film holder is caused to rotate in relation to the X-ray source.

2. The apparatus according to claim 1 wherein the reference is disposed on the major axis of the ellipse coinciding with the arc traced by the film holder.

3. The apparatus according to claim 2 wherein the cam connection between the second link and the reference takes the form of a pin and slot connection.

4. The apparatus according to claim 1 wherein the drive member takes the form of an elongated arm, and the means for shifting the axis of the same include an ellipsograph.

5. The apparatus according to claim 1 wherein the primary drive member rotates in a horizontal plane,

' nection between the links.

7. The apparatus according to claim 1 wherein the cam has a part cylindrical surface thereon.

8. The apparatus according to claim 7 wherein the surface of the cam has a concave recess therein.

9. The apparatus according to claim I wherein the film holder includes a cylindrical wheel, and the cam is yieldably biased into engagement with the wheel.

10. The apparatus according to claim 1 wherein the cam is disposed on the second link. 

1. In apparatus for recording a continuous X-ray picture of the dental arch, a fixed base, a drive member which is mounted to rotate opposite the base, and which is equipped with an X-ray source and an X-ray film holder on opposite sides of the rotational axis thereof, means operable to rotate the drive member, means operable during the rotation of the drive member to cause the rotational axis of the drive member to shift in relation to the base such that the source and the holder trace coaxial elliptical arcs, a fixed reference, and a pair of pivotally interconnected links, a first of which is pivotally connected with the drive member, and the second of which is cam connected with the reference, said film holder being rotatably mounted on the drive member, and there being a cam fixed on one of the links, and means on the drive member yieldably biasing the cam into engagement with the film holder so that on rotation of the drive member, the film holder is caused to rotate in relation to the X-ray source.
 2. The apparatus according to claim 1 wherein the reference is disposed on the major axis of the ellipse coinciding with the arc traced by the film holder.
 3. The apparatus according to claim 2 wherein the cam connection between the second link and the reference takes the form of a pin and slot connection.
 4. The apparatus according to claim 1 wherein the drive member takes the form of an elongated arm, and the means for shifting the axis of the same include an ellipsograph.
 5. The apparatus according to claim 1 wherein the primary drive member rotates in a horizontal plane, and the X-ray source and the film holder depend from the same.
 6. The apparatus according to claim 1 wherein the cam is curvilinear and disposed about the pivotal connection between the links.
 7. The apparatus according to claim 1 wherein the cam has a part cylindrical surface thereon.
 8. The apparatus according to claim 7 wherein the surface of the cam has a concave recess therein.
 9. The apparatus according to claim 1 wherein the film holder includes a cylindrical wheel, and the cam is yieldably biased into engagement with the wheel.
 10. The apparatus according to claim 1 wherein the cam is disposed on the second link. 